The present invention relates to a novel thermosetting resin composition which can provide excellent mechanical properties, particularly impact resistance and toughness, without impairing heat resistance.
Thermosetting resins having an imido structure provide excellent electrical insulating properties, heat resistance and dimensional stability to molded articles obtained therefrom. Therefore, they have been widely used in industrial fields.
However, while thermosetting resins obtained by using an aromatic bismaleimide are insoluble and unmeltable and have excellent heat resistance, they are inconveniently brittle and provide poor impact resistance and toughness. In order to eliminate these drawbacks, attempts have been made to use a thermosetting resin composition comprising an aromatic bismaleimide and an aromatic diamine. For example, polyaminobismaleimide resin (made by Rhone-Poulenc, trade name "Kelimide") comprising N,N'-4,4'-diphenylmethanebismaleimide and 4,4'-diaminodiphenylmethane has been widely used as an impregnating varnish, laminate and molded article (Japanese Patent Publication No. 46-23250). Unfortunately, this type of thermosetting resin composition still provides insufficient heat resistance and unsatisfactory impact resistance and toughness. In addition, 4,4'-diaminodiphenylmethane is toxic to humans.